Use helper methods for running pub.

sdk/lib/_internal/pub/test/pub_install_and_update_test.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library pub_tests;
 
 import 'dart:io';
 
 import 'package:scheduled_test/scheduled_test.dart';
 
 import 'descriptor.dart' as d;
 import 'test_pub.dart';
 
 main() {
   initConfig();
 
   forBothPubInstallAndUpdate((command) {
     group('requires', () {
       integration('a pubspec', () {
         d.dir(appPath, []).create();
 
         pubCommand(command,
-            error: new RegExp(r'^Could not find a file named "pubspec.yaml"'));
+            error: new RegExp(r'^Could not find a file named "pubspec.yaml" '
+                r'in the directory .*\.$'));
       });
 
       integration('a pubspec with a "name" key', () {
         d.dir(appPath, [
           d.pubspec({"dependencies": {"foo": null}})
         ]).create();
 
-        pubCommand(command, error: new RegExp(
-            r'^pubspec.yaml is missing the required "name" field '
-            r'\(e\.g\. "name: myapp"\)\.'));
+        pubCommand(command, error:
+            'pubspec.yaml is missing the required "name" field '
+            '(e.g. "name: myapp").');
       });
     });
 
     integration('adds itself to the packages', () {
       // The symlink should use the name in the pubspec, not the name of the
       // directory.
       d.dir(appPath, [
         d.pubspec({"name": "myapp_name"}),
         d.libDir('myapp_name')
       ]).create();
@@ skipping 61 matching lines @@
       ]).create();
 
       d.dir(appPath, [
         d.pubspec({"name": "myapp", "dependencies": {
           "foo": {"path": "../deps/foo"},
           "bar": {"path": "../deps/bar"}
         }})
       ]).create();
 
       pubCommand(command,
-          error: new RegExp(r"^Incompatible dependencies on 'baz':"));
+          error: new RegExp("^Incompatible dependencies on 'baz':\n"));
     });
   });
 }